The cutting knife of a crop cutting apparatus of the type with which the present invention is concerned generally comprises a horizontal support bar or flange supported on the apparatus for movement across the ground in a cutting action. On the support bar is mounted a plurality of guards with one guard section clamped above the support bar as a hold down and the other guard section providing a ledger surface for the knife blades clamped below the support bar.
Generally each lower guard section is formed as an integral cast body defining a one, two, three or more of forwardly projecting fingers which are connected by transverse bars.
The lower guard section can be of the type known as a stub guard where the front edge of the guard terminates at a position just behind the front edge of the blade. In this case, typically each stub guard has the fingers of the upper stub guard cooperating with the fingers of the lower stub guard to define a channel across the front of the support bar within which a reciprocating knife is guided.
The lower guard section can also be of the type known as a pointed guard where the front edge of the guard extends forwardly from the front edge of the blade. In this case, the upper guard portion cooperating with the forwardly projecting portions of the lower stub guard may include a single hold down finger at one of the forwardly projecting portions or at a location between the portions.
In one possible arrangement, the pointed guards do not include a section, commonly known as a tang, which extends over the ledger surface. In this case the hold down can be aligned with one of the forwardly projecting portions of the lower guard.
To obtain a proper cutting action it is necessary to adjust the spacing between the upper hold down and the ledger surface of the lower guard to accurately confine the knife and cause a cutting action between the knife blades and machined ledger surfaces on the lower guards. The adjustment must be controlled within narrow tolerances to optimize the cutting action without providing excessive frictional engagement between the ledger surface of the lower guards and the knife in its reciprocating movement.
Conventionally this adjustment is provided by shims which are inserted between the hold down and the support bar. However this technique is an inaccurate, inconvenient and time consuming process which must be regularly repeated during routine maintenance of the equipment in view of wear which occurs between the knife arrangement and the stub guards.
One arrangement is shown in U.S. Pat. No. 4,909,026 of the present Assignees where the adjustment between the stub guards of a sickle knife arrangement of a crop cutting apparatus is improved by the provision of an adjustment plate which is positioned between the upper stub guard and the support bar. The upper and lower stub guards are clamped onto the support bar by carriage bolts with the lower stub guard engaging against the under surface of the support bar and the upper stub guard engaging against the upper surface of the adjustment plate. The spacing and orientation of the adjustment plate relative to the support bar is adjusted by the three set screws which are threaded into the adjustment plate and engaged against the upper surface of the support bar.
Also in U.S. Pat. No. 7,373,769 (Talbot) assigned to the present assignees is shown a wear shield for the cutter bar of a crop harvesting machine where the cutter bar includes a guard bar mounted on a front edge of the cutter bar, a plurality of cutter guards carried on mounting bolts at spaced positions along the guard bar and a ground engaging bottom plate on the cutter bar extending rearwardly from the guard bar.
All publications, patents, and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent, or patent application was specifically and individually indicated to be incorporated by reference.